JP2019046561A - Power cable - Google Patents

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JP2019046561A
JP2019046561A JP2017165254A JP2017165254A JP2019046561A JP 2019046561 A JP2019046561 A JP 2019046561A JP 2017165254 A JP2017165254 A JP 2017165254A JP 2017165254 A JP2017165254 A JP 2017165254A JP 2019046561 A JP2019046561 A JP 2019046561A
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transmission cables
power transmission
ground
power cable
power
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大樹 兼田
Daiki Kaneda
大樹 兼田
晶二 真尾
Shoji Mashio
晶二 真尾
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Sumitomo Electric Industries Ltd
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Sumitomo Electric Industries Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B9/00—Power cables
    • H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
    • H01B7/26—Reduction of losses in sheaths or armouring
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/02—Cables with twisted pairs or quads
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
    • H01B7/20—Metal tubes, e.g. lead sheaths
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
    • H01B7/22—Metal wires or tapes, e.g. made of steel
    • H01B7/221—Longitudinally placed metal wires or tapes
    • H01B7/225—Longitudinally placed metal wires or tapes forming part of an outer sheath
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B9/00—Power cables
    • H01B9/003—Power cables including electrical control or communication wires
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B9/00—Power cables
    • H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
    • H01B9/028—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients with screen grounding means, e.g. drain wires

Abstract

To provide a power cable that suppresses iron loss and increases a transmission power.SOLUTION: A power cable 100 includes: a conductive wire; an insulation layer; and a conductive layer, in which three transmission cables 110R, 110Y and 110B arranged in a state where mutual semiconductive layers are in contact in a rotational symmetric position in a cross-sectional view; a binder 130 covering an outside surface of three grounding bus bars 120R, 120Y, 120B and three transmission cables; and a jacket arranged overlapping on the binder are contained. The three transmission cables have an outer diameter inscribing with a first circle having a diameter obtained by removing thicknesses of the binder and the jacket from a diameter of an envelope circle of a maximum power cable installable inside of a steel pipe 50 in a cross-sectional view. Three grounding bus bars protrude from the envelopment close curve of the three transmission cables in the cross-sectional view and has the diameter contained in the first circle.SELECTED DRAWING: Figure 1

Description

本発明は、電力ケーブルに関する。   The present invention relates to a power cable.

従来より、パイプタイプケーブルと呼ばれる、絶縁紙を巻いた３相の送電ケーブルを鋼管の内部に布設し、油に含浸させて絶縁を確保した送電ケーブルが米国を中心に広く利用されている。パイプタイプケーブルは、鋼管が経年劣化すると漏油に対応する保守費用や環境への影響が問題となるため、油を使わない架橋ポリエチレンケーブルへ置き換えが望まれている。   Conventionally, a power transmission cable called a pipe-type cable, in which a three-phase power transmission cable wrapped with insulating paper is laid in a steel pipe and impregnated with oil to ensure insulation, has been widely used mainly in the United States. Pipe-type cables are expected to be replaced with cross-linked polyethylene cables that do not use oil, because the maintenance costs and environmental impact of oil leaks become a problem when steel pipes deteriorate over time.

例えば、パイプタイプケーブルの置換え用として、NKT社のCityCable（登録商標）が実用化されている（非特許文献１参照）。   For example, NKT CityCable (registered trademark) has been put to practical use as a replacement for pipe type cables (see Non-Patent Document 1).

NKT Cables URL: http://www.cablejoints.co.uk/upload/NKT_Cables_Extra_High_Voltage_132kV_220kV_400kV_500kV___Brochure.pdf 平成２９年７月３１日検索NKT Cables URL: http://www.cablejoints.co.uk/upload/NKT_Cables_Extra_High_Voltage_132kV_220kV_400kV_500kV___Brochure.pdf Retrieved July 31, 2017

ところで、架橋ポリエチレンケーブルで絶縁を確保するには、絶縁紙よりも厚くする必要があり、架橋ポリエチレンケーブルを覆う金属遮蔽と防食層（PVC（polyvinyl chloride）やPE（polyethylene）製のシース）も必要である。   By the way, in order to ensure insulation with a cross-linked polyethylene cable, it is necessary to make it thicker than insulating paper, and a metal shield and anti-corrosion layer (PVC (polyvinyl chloride) or PE (polyethylene) sheath) covering the cross-linked polyethylene cable is also required. It is.

しかしながら、鋼管の内径は決まっているので、電気的に必要な絶縁層の厚さを維持するためには電力ケーブルの導体サイズを小さくする必要があり、置換えが実用化された例では、導体サイズは1000mm2未満に限られている。すなわち、送電ケーブルの外径には制限がある。 However, since the inner diameter of the steel pipe is fixed, it is necessary to reduce the conductor size of the power cable in order to maintain the electrically required insulation layer thickness. It is limited to less than 1000mm 2. That is, the outer diameter of the power transmission cable is limited.

また、パイプタイプケーブルには、外径制限の他に、鉄損によって送電容量が低下するという問題がある。磁性体パイプである鋼管に３相の送電ケーブルを３回対称の回転対称な位置に配置する場合の送電ケーブルの鉄損と導体内の損失の比率は一般に、次式（１）より求められる。このような式から求められることは、例えば、次の文献に記載されている。"The calculation of the temperature rise and load capability of cable system Year" 1957, Volume: 76, Issue: 3 Pages: 752 - 764, DOI: 10.1109/AIEEPAS.1957.4499653 ISSN: 0097-2460   In addition to the outer diameter limitation, the pipe type cable has a problem that the transmission capacity is reduced due to iron loss. In general, the ratio of the iron loss of the power transmission cable and the loss in the conductor when the three-phase power transmission cable is arranged in a three-fold rotationally symmetric position on the steel pipe, which is a magnetic pipe, is obtained from the following equation (1). What is obtained from such an equation is described in the following document, for example. "The calculation of the temperature rise and load capability of cable system Year" 1957, Volume: 76, Issue: 3 Pages: 752-764, DOI: 10.1109 / AIEEPAS.1957.4499653 ISSN: 0097-2460

Figure 2019046561
ここで、Ys: 電力ケーブルの交流導体抵抗に対する鉄損率、S: 電力ケーブルの相間距離 (inch)、Dp: 鉄管の内径 (inch)、Rac: 電力ケーブルの交流導体抵抗 (/feet)である。345kVで 3500kcmil、絶縁厚が１インチの導体の場合、S=4.2 inch, Dp=10.25 inch, Rac=4.00/feetとすると、式（１）より鉄損率Ysは 0.88となる。
Figure 2019046561
 Where Ys is the iron loss ratio relative to the AC conductor resistance of the power cable, S is the interphase distance of the power cable (inch), Dp is the inner diameter of the iron pipe (inch), and Rac is the AC conductor resistance of the power cable (/ feet). . In the case of a conductor of 345 kV, 3500 kcmil, and insulation thickness of 1 inch, assuming that S = 4.2 inch, Dp = 10.25 inch, Rac = 4.00 / feet, the iron loss ratio Ys is 0.88 from equation (1).

すなわち、導体損失の８８％もの損失が鋼管の内部で発生するため、送電ケーブルが発熱し、鋼管の内部に配置しない場合の電力ケーブルの架橋ポリエチレンケーブルよりも損失が多くなり、不経済であり、許容電流が低下する欠点があった。   That is, as much as 88% of the conductor loss occurs inside the steel pipe, the power transmission cable generates heat, and the loss is higher than the cross-linked polyethylene cable of the power cable when not arranged inside the steel pipe, which is uneconomical, There was a drawback that the allowable current was reduced.

そこで、鉄損を抑制するとともに、送電電力を増大させた電力ケーブルを提供することを目的とする。   Then, it aims at providing the power cable which suppressed iron loss and increased transmission power.

本発明の実施の形態の電力ケーブルは、基準電位点に接続される鋼管の内部に敷設される電力ケーブルであって、三相交流電力を伝送する導電線と、前記導電線を被覆する絶縁層と、前記絶縁層を被覆する半導電層とを有する３本の送電ケーブルであって、断面視で前記３本の送電ケーブルの中心に対する３回対称の回転対称な位置において互いの前記半導電層同士が接した状態で配置される３本の送電ケーブルと、３本の接地母線であって、それぞれが前記３本の送電ケーブルのうちの隣り合う２本の外周面に接して、前記中心に対する３回対称の回転対称な位置に配置される３本の接地母線と、前記３本の接地母線及び前記３本の送電ケーブルの外側面を覆うバインダと、前記バインダに重ねて配置されるジャケットとを含み、前記３本の送電ケーブルは、断面視で前記鋼管の内部に敷設可能な最大の電力ケーブルの包絡円の半径から前記バインダ及び前記ジャケットの厚さを除いた半径を有する第１円に内接する外径を有し、前記３本の接地母線は、断面視で３本の送電ケーブルの包絡閉曲線よりも突出し、前記第１円に収まる外径を有する。   A power cable according to an embodiment of the present invention is a power cable laid inside a steel pipe connected to a reference potential point, and includes a conductive wire that transmits three-phase AC power, and an insulating layer that covers the conductive wire And a semiconductive layer covering the insulating layer, wherein the semiconductive layers are mutually in a rotationally symmetrical position that is three-fold symmetric with respect to the center of the three power cables in a cross-sectional view. Three power transmission cables arranged in contact with each other and three ground buses, each in contact with two adjacent outer peripheral surfaces of the three power transmission cables, with respect to the center Three ground buses arranged at rotationally symmetric positions that are three-fold symmetric, a binder that covers the outer surfaces of the three ground buses and the three power transmission cables, and a jacket that is placed on the binder. Including the three The power transmission cable has an outer diameter inscribed in a first circle having a radius excluding the thickness of the binder and the jacket from the radius of the envelope circle of the largest power cable that can be laid in the steel pipe in a cross-sectional view. The three ground buses protrude from the envelope closed curve of the three power transmission cables in a cross-sectional view and have an outer diameter that fits in the first circle.

鉄損を抑制するとともに、送電電力を増大させた電力ケーブルを提供することができる。   It is possible to provide a power cable that suppresses iron loss and increases transmission power.

実施の形態の電力ケーブル１００を示す図である。It is a figure showing electric power cable 100 of an embodiment. 実施の形態の電力ケーブル１００の送電ケーブル１１０を示す図である。It is a figure which shows the power transmission cable 110 of the power cable 100 of embodiment. 送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの位置関係を示す図である。It is a figure which shows the positional relationship of power transmission cable 110R, 110Y, 110B and the earthing | grounding buses 120R, 120Y, 120B. 導線１１１Ｒ、接地母線１２０Ｒ、仮想接地流路１０Ａに流れる電流と磁界の関係を示す図である。It is a figure which shows the relationship of the electric current and magnetic field which flow through conducting wire 111R, the earthing | grounding bus line 120R, and the virtual earthing flow path 10A. 実施の形態の変形例の電力ケーブル１００Ｍの断面を示す図である。It is a figure which shows the cross section of the power cable 100M of the modification of embodiment. 導線１１１Ｒ、１１１Ｙ、１１１Ｂに流れる電流Icと、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂに流れる循環電流IECCとの幾何学的中心位置を示す図である。It is a figure which shows the geometrical center position of the electric current Ic which flows into conducting wire 111R, 111Y, 111B, and the circulating current I ECC which flows into earth | ground buses 120R, 120Y, 120B. 電力ケーブル１００及び１００Ｍと、比較用の電力ケーブルとの接地母線の断面積、電流比、接地母線の発熱量、鋼管５０の外表面での磁界、及び鉄損を示す図である。It is a figure which shows the cross-sectional area of the grounding bus | bath of electric power cables 100 and 100M, and a comparison electric power cable, an electric current ratio, the emitted-heat amount of a grounding bus | bath, the magnetic field in the outer surface of the steel pipe 50, and an iron loss.

以下、本発明の電力ケーブルを適用した実施の形態について説明する。   Embodiments to which the power cable of the present invention is applied will be described below.

＜実施の形態＞
図１は、実施の形態の電力ケーブル１００を示す図であり、（Ａ）は斜視図、（Ｂ）は断面図である。なお、図１（Ａ）の斜視図は、電力ケーブル１００を長手方向に対して垂直な面に沿って切断した状態を示す。 <Embodiment>
1A and 1B are diagrams illustrating a power cable 100 according to an embodiment, where FIG. 1A is a perspective view and FIG. 1B is a cross-sectional view. Note that the perspective view of FIG. 1A shows a state where the power cable 100 is cut along a plane perpendicular to the longitudinal direction.

電力ケーブル１００は、鋼管５０の内部に敷設されており、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂ、バインダ１３０、防食層１４０、及び樹脂部材１５０を含む。電力ケーブル１００は、２つの変電所の間に設けられている。   The power cable 100 is laid inside the steel pipe 50 and includes power transmission cables 110R, 110Y, 110B, ground buses 120R, 120Y, 120B, a binder 130, an anticorrosion layer 140, and a resin member 150. The power cable 100 is provided between the two substations.

鋼管５０は、例えば、鉄製のパイプであり、内部には送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂ、バインダ１３０、及び防食層１４０が挿通される。鋼管５０は、基準電位点に接続される。実施の形態では、一例として、鋼管５０は接地され、グランド電位に保持される。鋼管５０を基準電位に保持するのは、送電ケーブル１１０に地絡等による事故電流が生じた場合に、鋼管５０を事故電流の通流経路にするためである。   The steel pipe 50 is, for example, an iron pipe, and the power transmission cables 110R, 110Y, 110B, the ground buses 120R, 120Y, 120B, the binder 130, and the anticorrosion layer 140 are inserted therein. The steel pipe 50 is connected to a reference potential point. In the embodiment, as an example, the steel pipe 50 is grounded and held at the ground potential. The reason why the steel pipe 50 is held at the reference potential is to make the steel pipe 50 a current-carrying path for the accident current when an accident current due to a ground fault or the like occurs in the power transmission cable 110.

鋼管５０は、未使用の新品の鋼管であってもよいが、既使用の中古の鋼管であってもよい。例えば、既設の電力ケーブルを実施の形態の電力ケーブル１００に交換する場合には、既設の電力ケーブルの鋼管５０を再利用してもよい。   The steel pipe 50 may be an unused new steel pipe, or may be an already-used used steel pipe. For example, when replacing an existing power cable with the power cable 100 of the embodiment, the steel pipe 50 of the existing power cable may be reused.

より具体的には、例えば、既設のＰＯＦ(Pipe type Oil Filled)ケーブル（油浸型ケーブル）の送電ケーブル及び絶縁油を取り除いて洗浄した鋼管を鋼管５０として利用してもよい。実施の形態では、既設のＰＯＦケーブルの鋼管を鋼管５０として利用する形態について説明する。鋼管５０の内径は、一例として２６０．３５ｍｍ（１０．２５インチ）である。   More specifically, for example, an existing POF (Pipe type Oil Filled) cable (oil-immersion type cable) power transmission cable and a steel pipe cleaned by removing insulating oil may be used as the steel pipe 50. In the embodiment, an embodiment in which a steel pipe of an existing POF cable is used as the steel pipe 50 will be described. As an example, the inner diameter of the steel pipe 50 is 260.35 mm (10.25 inches).

送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、仮想的な中心線１０を中心として、断面視における３回対称の回転対称な位置関係に配置され、中心線１０に沿って周囲に撚り合わされている。送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、三相の交流電力を送電するために用いられ、それぞれ、各相の電力を伝送する。送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、３本の送電ケーブルの一例である。   The power transmission cables 110 </ b> R, 110 </ b> Y, and 110 </ b> B are arranged in a rotationally symmetrical positional relationship that is three-fold symmetric in a sectional view around the virtual center line 10, and are twisted around the center line 10. The power transmission cables 110R, 110Y, and 110B are used to transmit three-phase AC power, and transmit power for each phase. The power transmission cables 110R, 110Y, and 110B are examples of three power transmission cables.

送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、断面視で鋼管５０の内部に敷設可能な最大の電力ケーブルの包絡円の半径からバインダ１３０及び防食層１４０の厚さを除いた半径を有する円１３０Ａに、断面視で中心線１０を中心とした３回対称の回転対称な位置関係に配置した状態で内接する外径を有する。鋼管５０の内径という制約の中で、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの断面積を最大化するためである。   The transmission cables 110R, 110Y, and 110B have a cross section of a circle 130A having a radius excluding the thickness of the binder 130 and the anticorrosion layer 140 from the radius of the envelope circle of the largest power cable that can be laid inside the steel pipe 50 in a cross sectional view. It has an outer diameter that is inscribed in a state of being arranged in a rotationally symmetrical positional relationship that is three-fold symmetric about the center line 10 as viewed. This is for maximizing the cross-sectional areas of the power transmission cables 110R, 110Y, and 110B within the restriction of the inner diameter of the steel pipe 50.

なお、包絡円は、断面視で鋼管５０の内部に敷設可能な最大の電力ケーブルの断面を含む最小の円である。このような包絡円の直径は、一例として長さが６０９．６０ｍ（２０００フィート）であり、内径が１５５．８ｍｍ（６．１２５インチ）から２６０．３５ｍｍ（１０．２５インチ）である鋼管５０に、長さが６０９．６０ｍ（２０００フィート）以上ある電力ケーブル１００を挿通させるのに必要な余裕代（マージン）を、鋼管５０の内径から差し引いて得る寸法である。   The envelope circle is the smallest circle including a cross section of the largest power cable that can be laid inside the steel pipe 50 in a sectional view. The diameter of such an envelope circle is, for example, a steel pipe 50 having a length of 609.60 m (2000 feet) and an inner diameter of 155.8 mm (6.125 inches) to 260.35 mm (10.25 inches). This is a dimension obtained by subtracting a margin (margin) necessary for inserting the power cable 100 having a length of 609.60 m (2000 feet) or more from the inner diameter of the steel pipe 50.

また、円１３０Ａは、バインダ１３０及び防食層１４０の厚さを除いて、鋼管５０の内部に挿通させることが可能な最大の外径を有する送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂが内接する円であり、断面視でバインダ１３０の内周面が規定する円である。   Further, the circle 130A is a circle inscribed by the power transmission cables 110R, 110Y, and 110B having the maximum outer diameter that can be inserted into the steel pipe 50 except for the thickness of the binder 130 and the anticorrosion layer 140. It is a circle defined by the inner peripheral surface of the binder 130 in a cross-sectional view.

送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、例えば、それぞれ、赤相、黄相、青相と区別される。送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、色が異なるが互いに同様の構成を有する。このため、以下の説明において送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂを区別しない場合には、単に送電ケーブル１１０と称す。送電ケーブル１１０の詳細な構成については、図２を用いて後述する。   The power transmission cables 110R, 110Y, and 110B are distinguished from, for example, a red phase, a yellow phase, and a blue phase, respectively. The power transmission cables 110R, 110Y, and 110B have the same configuration but different colors. For this reason, in the following description, when the power transmission cables 110R, 110Y, and 110B are not distinguished, they are simply referred to as the power transmission cable 110. A detailed configuration of the power transmission cable 110 will be described later with reference to FIG.

接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、接地電位に保持される導体製（例えば、アルミニウム製又は銅製）のワイヤである。接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、それぞれ、細い複数のワイヤを撚り合わせて１本にしたワイヤである。接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、外側面を覆う絶縁層等の遮蔽物や防食層を有さず、導体が剥き出しのワイヤである。接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、事故時に変電所に電流を流すために設けられている。接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの各々の両端は、接地されている。   The ground buses 120R, 120Y, and 120B are wires made of a conductor (for example, made of aluminum or copper) that are held at a ground potential. Each of the ground buses 120R, 120Y, and 120B is a wire obtained by twisting a plurality of thin wires into one. The ground buses 120R, 120Y, and 120B are wires that do not have a shield or an anticorrosion layer such as an insulating layer that covers the outer surface and are exposed from the conductor. The ground buses 120R, 120Y, and 120B are provided to allow current to flow to the substation in the event of an accident. Both ends of each of the ground buses 120R, 120Y, 120B are grounded.

接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの外周面に接触する形で、断面視で中心線１０を中心として３回対称の回転対称な位置関係に配置されている。接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、それぞれ、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの対角位置に配置される。   The ground buses 120R, 120Y, and 120B are arranged in a rotationally symmetrical positional relationship that is three-fold symmetric about the center line 10 in a cross-sectional view, in contact with the outer peripheral surfaces of the power transmission cables 110R, 110Y, and 110B. The ground buses 120R, 120Y, and 120B are disposed at diagonal positions of the power transmission cables 110R, 110Y, and 110B, respectively.

より具体的には、接地母線１２０Ｒは、送電ケーブル１１０Ｙ、１１０Ｂの外周面の谷間に嵌め込まれており、接地母線１２０Ｂは、送電ケーブル１１０Ｒ、１１０Ｙの外周面の谷間に嵌め込まれており、接地母線１２０Ｙは、送電ケーブル１１０Ｂ、１１０Ｒの外周面の谷間に嵌め込まれている。   More specifically, the ground bus 120R is fitted in the valleys of the outer peripheral surfaces of the power transmission cables 110Y and 110B, and the ground bus 120B is fitted in the valleys of the outer peripheral surfaces of the power transmission cables 110R and 110Y. 120Y is fitted in the valleys of the outer peripheral surfaces of the power transmission cables 110B and 110R.

接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、両端で互いに接続されることによって、互いに電気的に接続されており、三角柱状の閉ループを構成する。接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの最外周の半導電性ベッディングに接触することにより、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの表面を接地している。   The ground buses 120R, 120Y, and 120B are electrically connected to each other by being connected to each other at both ends, thereby forming a triangular prism-shaped closed loop. The ground buses 120R, 120Y, 120B are in contact with the outermost semiconductive bedding of the power transmission cables 110R, 110Y, 110B, thereby grounding the surfaces of the power transmission cables 110R, 110Y, 110B.

また、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、円１３０Ａに接する外径を有する。すなわち、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、バインダ１３０の内周面に接している。このため、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０Ｒ、１２０Ｙ、１２０Ｂのうち、断面視で中心線１０から見て径方向に最も突出している部分は、円１３０Ａ上に位置する。   Further, the ground buses 120R, 120Y, 120B have outer diameters in contact with the circle 130A. That is, the ground buses 120R, 120Y, and 120B are in contact with the inner peripheral surface of the binder 130. For this reason, among the power transmission cables 110R, 110Y, and 110B and the ground buses 120R, 120Y, and 120B, the portion that protrudes most in the radial direction when viewed from the center line 10 in a cross-sectional view is located on the circle 130A.

接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外側面に絶縁層等の被覆を設けずに、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂが円１３０Ａに接する外径を有する構成にするのは、上述した包絡円の中で、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの外周部に余った空間内で、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外径を最大化するとともに、半導電性ベッディングを介して送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの表面を接地するためである。なお、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの表面は、導線１１１から供給され絶縁層１１３を経由して漏れ出る通称充電電流により絶縁層１１３の表面電位が浮遊する現象が生じるため、長手方向の接地だけでなく半径方向に接地が必要である。送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂと接触していることによって、径方向において接地されている。   In the envelope circle described above, the ground buses 120R, 120Y, 120B have an outer diameter in contact with the circle 130A without providing a coating such as an insulating layer on the outer surface of the ground buses 120R, 120Y, 120B. In the space remaining on the outer periphery of the power transmission cables 110R, 110Y, 110B, the outer diameter of the ground buses 120R, 120Y, 120B is maximized, and the surfaces of the power transmission cables 110R, 110Y, 110B through the semiconductive bedding This is for grounding. The surface of the power transmission cables 110R, 110Y, and 110B has a phenomenon that the surface potential of the insulating layer 113 floats due to a so-called charging current that is supplied from the conductive wire 111 and leaks through the insulating layer 113. Instead, grounding in the radial direction is required. The power transmission cables 110R, 110Y, and 110B are grounded in the radial direction by contacting the ground buses 120R, 120Y, and 120B.

なお、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、互いに同様の構成を有するため、以下の説明において接地母線１２０Ｒ、１２０Ｙ、１２０Ｂを区別しない場合には、単に接地母線１２０と称す。   Since the ground buses 120R, 120Y, and 120B have the same configuration, the ground buses 120R, 120Y, and 120B are simply referred to as the ground bus 120 in the following description unless they are distinguished from each other.

バインダ１３０は、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ及び接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外側面を覆うことで、これらを縛る（束ねる）バインダテープであり、絶縁層である。   The binder 130 is a binder tape that covers and binds the outer surfaces of the power transmission cables 110R, 110Y, and 110B and the ground buses 120R, 120Y, and 120B, and is an insulating layer.

防食層１４０は、バインダ１３０に重ねて設けられ、バインダ１３０を介して送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ及び接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外側面を覆う絶縁層である。   The anticorrosion layer 140 is an insulating layer that is provided so as to overlap the binder 130 and covers the outer surfaces of the power transmission cables 110R, 110Y, 110B and the ground buses 120R, 120Y, 120B via the binder 130.

樹脂部材１５０は、バインダ１３０及び防食層１４０の内部で、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの間に配置されている。樹脂部材１５０は、絶縁材料製であり、例えば、ポリプロピレン製の紐状の部材である。   The resin member 150 is disposed between the power transmission cables 110R, 110Y, and 110B and the ground buses 120R, 120Y, and 120B inside the binder 130 and the anticorrosion layer 140. The resin member 150 is made of an insulating material, for example, a polypropylene string-like member.

樹脂部材１５０は、バインダ１３０及び防食層１４０の内部で、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの隙間を埋め、断面視でバインダ１３０の内周面が規定する閉曲線が円になるように、敷き詰められている。   The resin member 150 fills the gaps between the transmission cables 110R, 110Y, 110B and the ground buses 120R, 120Y, 120B inside the binder 130 and the anticorrosion layer 140, and the closed curve defined by the inner peripheral surface of the binder 130 in a cross-sectional view is a circle. It is laid down to become.

次に、図２を用いて、送電ケーブル１１０の詳細な構成について説明する。   Next, a detailed configuration of the power transmission cable 110 will be described with reference to FIG.

図２は、実施の形態の電力ケーブル１００の送電ケーブル１１０を示す図であり、（Ａ）は断面図、（Ｂ）はトリプレックス構造を示す斜視図である。図２（Ｂ）には、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂに加えて接地母線１２０Ｒ、１２０Ｙ、１２０Ｂも示す。   2A and 2B are diagrams illustrating a power transmission cable 110 of the power cable 100 according to the embodiment, where FIG. 2A is a cross-sectional view and FIG. 2B is a perspective view illustrating a triplex structure. FIG. 2B also shows ground buses 120R, 120Y, and 120B in addition to power transmission cables 110R, 110Y, and 110B.

図２（Ａ）に示すように、送電ケーブル１１０は、導線１１１、導線スクリーン１１２、絶縁層１１３、絶縁スクリーン１１４、及び半導電性ベッディング１１５を含む。   As shown in FIG. 2A, the power transmission cable 110 includes a conductive wire 111, a conductive wire screen 112, an insulating layer 113, an insulating screen 114, and a semiconductive bedding 115.

導線１１１は、金属製であり、例えば、銅線を用いることができる。導線１１１は、送電ケーブル１１０のうち送電を行う導体である。導線１１１は、細い複数の銅線を撚り合わせて１本にしたワイヤ状の導線である。   The conducting wire 111 is made of metal, and for example, a copper wire can be used. The conducting wire 111 is a conductor that transmits power in the power transmission cable 110. The conducting wire 111 is a wire-like conducting wire obtained by twisting a plurality of thin copper wires into one.

導線スクリーン１１２は、耐熱性のある半導電性のテープや、カーボン粉末を含有する樹脂層とで構成され、導線１１１の周囲に巻回される。耐熱性のある半導電性のテープとしては、例えば、ナイロンやポリエステルを用いることができ、導体粉末を含有する樹脂層としては、例えば、ＥＥＡ（Ethylene-Ethylacrylate Copolymer）樹脂を用いることができる。   The conductive wire screen 112 is composed of a heat-resistant semiconductive tape or a resin layer containing carbon powder, and is wound around the conductive wire 111. For example, nylon or polyester can be used as the semiconductive tape having heat resistance, and EEA (Ethylene-Ethylacrylate Copolymer) resin can be used as the resin layer containing the conductor powder.

絶縁層１１３は、導線１１１を絶縁するために設けられている。絶縁層１１３は、例えば、ＸＬＰＥ(Crosslinked polyethylene:架橋ポリエチレン)を用いて射出成形で作製することができる。ここでは、絶縁層１１３としてＸＬＰＥを用いる形態について説明するが、耐熱性と絶縁性がある材料であれば、ＸＬＰＥ以外の材料を絶縁層１１３として用いてもよい。   The insulating layer 113 is provided to insulate the conductive wire 111. The insulating layer 113 can be manufactured by injection molding using, for example, XLPE (Crosslinked polyethylene). Here, a mode in which XLPE is used for the insulating layer 113 will be described; however, a material other than XLPE may be used for the insulating layer 113 as long as the material has heat resistance and insulating properties.

絶縁スクリーン１１４は、カーボン粉末を含有する樹脂層で構成され、絶縁層１１３の周囲に巻回される。カーボン粉末を含有する樹脂層としては、例えば、ＥＥＡ樹脂を用いることができる。   The insulating screen 114 is composed of a resin layer containing carbon powder, and is wound around the insulating layer 113. As the resin layer containing carbon powder, for example, an EEA resin can be used.

ベッディング１１５は、所謂ベッディングテープであり、半導電座床である。ベッディング１１５は、絶縁スクリーン１１４の周囲に巻回される。   The bedding 115 is a so-called bedding tape and is a semiconductive floor. The bedding 115 is wound around the insulating screen 114.

以上のような構成を有する送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ（図１（Ａ）、（Ｂ）参照）は、図２（Ｂ）に示すように、中心線１０を中心として、中心線１０の長手方向に沿って撚り合わされる。このような３本の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂを撚り合わせた構造をトリプレックス構造(Triplex formation)と称す。   The transmission cables 110R, 110Y, and 110B (see FIGS. 1 (A) and (B)) having the above-described configuration are, as illustrated in FIG. Twisted along the direction. Such a structure in which the three power transmission cables 110R, 110Y, and 110B are twisted together is referred to as a triplex structure.

また、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの周囲に撚り合わされている。   The ground buses 120R, 120Y, and 120B are twisted around the power transmission cables 110R, 110Y, and 110B.

送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂのトリプレックス構造は、断面視で、中心線１０を中心とする３回対称の回転対称な位置関係を保ちながら、中心線１０の周囲に撚り合わされる構造である。トリプレックス構造は、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの長手方向における伸縮が少なく、電力ケーブル１００同士を接続するマンホール内での固定が容易になる構造である。   The triplex structure of the power transmission cables 110 </ b> R, 110 </ b> Y, and 110 </ b> B is a structure that is twisted around the center line 10 while maintaining a three-fold rotationally symmetrical positional relationship around the center line 10 in a cross-sectional view. The triplex structure is a structure in which the power transmission cables 110R, 110Y, and 110B are less stretched in the longitudinal direction, and can be easily fixed in the manhole connecting the power cables 100.

なお、断面視における３回対称の回転対称な位置関係とは、完全な３回対称の回転対称な位置関係に限らず、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの撚り合わせにおけるばらつき等による位置ずれが生じていても、断面視における３回対称の回転対称な位置関係が保たれているものとして取り扱う。   Note that the three-fold rotationally symmetric positional relationship in the cross-sectional view is not limited to the complete three-fold rotationally symmetric positional relationship, and a positional shift due to variations in twisting of the power transmission cables 110R, 110Y, and 110B occurs. Even in such a case, it is assumed that the rotationally symmetrical positional relationship of three-fold symmetry in the sectional view is maintained.

実施の形態では、中心線１０の外周に沿って、トリプレックス構造の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂを配置し、さらにその外周に接地母線１２０Ｒ、１２０Ｙ、１２０Ｂを撚り合わせて、バインダ１３０及び防食層１４０で覆った状態で、電力ケーブル１００を鋼管５０（図１（Ａ），（Ｂ）参照）の内部に配置する。   In the embodiment, power transmission cables 110R, 110Y, 110B having a triplex structure are arranged along the outer periphery of the center line 10, and the ground buses 120R, 120Y, 120B are twisted around the outer periphery of the transmission cables 110R, 110Y, 120B. In a state covered with 140, the power cable 100 is disposed inside the steel pipe 50 (see FIGS. 1A and 1B).

以上のような実施の形態の電力ケーブル１００は、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ（図１（Ａ），（Ｂ）参照）で三相交流電力を伝送する。定格容量は、一例として、８００ＭＶＡ（３４５ｋＶ，１３３９Ａ）である。ただし、この定格容量は一例に過ぎず、敷設条件(温度や鋼管の埋設深さ)によって変わるものである。   The power cable 100 according to the embodiment as described above transmits three-phase AC power using the power transmission cables 110R, 110Y, and 110B (see FIGS. 1A and 1B). As an example, the rated capacity is 800 MVA (345 kV, 1339 A). However, this rated capacity is only an example and varies depending on the laying conditions (temperature and embedment depth of the steel pipe).

電力ケーブル１００は、一例として、長さが６０９．６０ｍ（２０００フィート）であり、複数の電力ケーブル１００を直列に接続して用いる。この場合に、各電力ケーブル１００の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、同じ色同士のものが接続される。送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂについて、同じ色同士のものを接続するとは、同じ色の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの導線１１１同士を接続することである。   For example, the power cable 100 has a length of 609.60 m (2000 feet), and a plurality of power cables 100 are connected in series. In this case, the power cables 110R, 110Y, and 110B of each power cable 100 are connected with the same color. Connecting power transmission cables 110R, 110Y, and 110B having the same color means connecting the conductive wires 111 of power transmission cables 110R, 110Y, and 110B having the same color.

電力ケーブル１００は、既設の鋼管５０の内部で直列接続された複数の電力ケーブルのうちの一部を交換する際に、交換用の新たな電力ケーブルとして用いることができる。例えば、直列接続された既設の複数の電力ケーブルのうちのある１本の電力ケーブルを交換する場合に、電力ケーブル１００を用いてもよい。この場合に、取り除かれる電力ケーブルが鋼管５０と同様の鋼管を有し、内部に電力ケーブル１００を挿通可能である場合には、取り除かれる電力ケーブルの鋼管を鋼管５０として用いることができる。   The power cable 100 can be used as a new power cable for replacement when a part of the plurality of power cables connected in series inside the existing steel pipe 50 is replaced. For example, the power cable 100 may be used when replacing one power cable among a plurality of existing power cables connected in series. In this case, when the power cable to be removed has a steel pipe similar to the steel pipe 50 and the power cable 100 can be inserted therein, the steel pipe of the power cable to be removed can be used as the steel pipe 50.

また、上述の場合には、電力ケーブル１００の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの導線１１１を電力ケーブル１００の両端にある既設の電力ケーブルの対応する相（同じ色の相）の送電ケーブルの導線と接続すればよい。また、この場合に、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、変電所で基準電位の接地点に接地される。   Moreover, in the above-mentioned case, the conducting wire 111 of the power transmission cable 110R, 110Y, 110B of the power cable 100 is replaced with the conducting wire of the power transmission cable of the corresponding phase (the same color phase) of the existing power cable at both ends of the power cable 100. Just connect. In this case, the ground buses 120R, 120Y, and 120B are grounded to the ground point of the reference potential at the substation.

図３は、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの位置関係を示す図である。図３には、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの導線１１１を区別して、導線１１１Ｒ、１１１Ｙ、１１１Ｂとして示す。   FIG. 3 is a diagram illustrating a positional relationship between the power transmission cables 110R, 110Y, and 110B and the ground buses 120R, 120Y, and 120B. In FIG. 3, the conducting wires 111 of the power transmission cables 110R, 110Y, and 110B are distinguished and shown as conducting wires 111R, 111Y, and 111B.

また、断面視における送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ及び接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの中心を通る仮想接地流路１０Ａを示す。仮想接地流路１０Ａは、図１（Ａ）、（Ｂ）に示す中心線１０上に位置する。仮想接地流路１０Ａは、電力ケーブル１００の両端で接地母線１２０Ｒ、１２０Ｙ、１２０Ｂに接続される仮想の流路であり、接地電位に保持される。   Further, a virtual ground channel 10A passing through the centers of the power transmission cables 110R, 110Y, 110B and the ground buses 120R, 120Y, 120B in a cross-sectional view is shown. The virtual ground channel 10A is located on the center line 10 shown in FIGS. The virtual ground channel 10A is a virtual channel that is connected to the ground buses 120R, 120Y, and 120B at both ends of the power cable 100, and is held at the ground potential.

ここで、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、互いに同様の構成を有し、仮想接地流路１０Ａに対して回転対称の位置に配置されているため、図３に加えて図４を用いて接地母線１２０Ｒについて検討する。   Here, since the ground buses 120R, 120Y, and 120B have the same configuration and are arranged at rotationally symmetric positions with respect to the virtual ground channel 10A, the ground buses 120R, 120Y, and 120B are grounded using FIG. 4 in addition to FIG. Consider the bus 120R.

図４は、導線１１１Ｒ、接地母線１２０Ｒ、仮想接地流路１０Ａに流れる電流と磁界の関係を示す図である。接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの各々の両端は、接地されているため、図４では接地母線１２０Ｒの両端に接地の記号を記す。   FIG. 4 is a diagram showing the relationship between the current flowing in the conductive wire 111R, the ground bus 120R, and the virtual ground flow path 10A and the magnetic field. Since both ends of each of the ground buses 120R, 120Y, and 120B are grounded, in FIG. 4, a ground symbol is shown at both ends of the ground bus 120R.

接地母線１２０Ｒと仮想接地流路１０Ａは、破線で示す閉ループ１２１を構築する。導線１１１Ｒに矢印で示す下向きの電流１１１Ｒ１が流れると、右ねじの法則に従って磁界１１１Ｒ２が生じる。このため、接地母線１２０Ｒには磁界１１１Ｒ２を打ち消す方向の磁界１２０Ａが生じ、磁界１２０Ａによって接地母線１２０Ｒには下向きの電流１２０Ａ１が生じ、この結果、電流１２０Ａ１が閉ループ１２１に流れる。電流１２０Ａ１は誘導電流であり、循環電流である。   The ground bus 120R and the virtual ground channel 10A constitute a closed loop 121 indicated by a broken line. When a downward current 111R1 indicated by an arrow flows through the conducting wire 111R, a magnetic field 111R2 is generated according to the right-handed screw law. Therefore, a magnetic field 120A is generated in the direction of canceling the magnetic field 111R2 in the ground bus 120R, and a downward current 120A1 is generated in the ground bus 120R by the magnetic field 120A. As a result, the current 120A1 flows in the closed loop 121. The current 120A1 is an induced current and a circulating current.

ここでは、導線１１１Ｒ、接地母線１２０Ｒ、及び仮想接地流路１０Ａの関係を用いて、三相交流（Ｒ、Ｙ、Ｂ）のうちの１相について示したが、導線１１１Ｙ、接地母線１２０Ｙ、及び仮想接地流路１０Ａと、導線１１１Ｂ、接地母線１２０Ｂ、及び仮想接地流路１０Ａとについても、同様の関係が生じる。   Here, one phase of the three-phase alternating current (R, Y, B) is shown by using the relationship between the conducting wire 111R, the grounding bus 120R, and the virtual grounding flow path 10A, but the conducting wire 111Y, the grounding bus 120Y, and The same relationship also occurs between the virtual ground channel 10A, the conductive wire 111B, the ground bus 120B, and the virtual ground channel 10A.

仮想接地流路１０Ａには、三相交流（Ｒ、Ｙ、Ｂ）による１２０度づつ位相の異なる循環電流が流れるため、仮想接地流路１０Ａに流れる合計の電流はゼロになる。従って、仮想接地流路１０Ａを用いた仮想接地が成り立つ。   In the virtual ground flow path 10A, circulating currents having different phases by 120 degrees due to three-phase alternating current (R, Y, B) flow, so that the total current flowing in the virtual ground flow path 10A becomes zero. Therefore, virtual grounding using the virtual grounding channel 10A is established.

ここで、導線１１１Ｒに流れる電流１１１Ｒ１によって生じる磁界１１１Ｒ２と、接地母線１２０Ｒに生じる磁界１１１Ｒ２とは、閉ループ１２１を貫き、お互いに磁界を打ち消す方向に発生するが、接地母線１２０Ｒの交流抵抗により位相差が生じる。   Here, the magnetic field 111R2 generated by the current 111R1 flowing in the conducting wire 111R and the magnetic field 111R2 generated in the ground bus 120R pass through the closed loop 121 and cancel each other out, but the phase difference is caused by the AC resistance of the ground bus 120R. Occurs.

循環電流（電流１２０Ａ１）をIECC (A)、導線１１１Ｒに流れる電流１１１Ｒ１をIc (A)、交流の角周波数をω、導線１１１Ｒと接地母線１２０Ｒとの相互インピーダンスをM (Ω/m)、接地母線１２０Ｒの交流抵抗をRECC (Ω/m)、接地母線１２０ＲのリアクタンスをXECC (Ω/m)とすると、循環電流IECCは近似的に次式（２）で求めることができる。 The circulating current (current 120A1) is I ECC (A), the current 111R1 flowing through the conductor 111R is Ic (A), the AC angular frequency is ω, the mutual impedance between the conductor 111R and the ground bus 120R is M (Ω / m), If the AC resistance of the ground bus 120R is R ECC (Ω / m) and the reactance of the ground bus 120R is X ECC (Ω / m), the circulating current I ECC can be approximately calculated by the following equation (2).

Figure 2019046561
循環電流IECCを最大化するには、接地母線１２０ＲのリアクタンスXECCを最小化すればよい。リアクタンスXECCは、次式（３）で表される。ここで、交流電力の周波数をｆ (Hz)、接地母線１２０Ｒの外径をr (mm)、接地母線１２０Ｒの中心と、仮想接地流路１０Ａの距離をD (mm)とする。
Figure 2019046561
 In order to maximize the circulating current I ECC , the reactance X ECC of the ground bus 120R may be minimized. The reactance X ECC is expressed by the following equation (3). Here, the frequency of AC power is f (Hz), the outer diameter of the ground bus 120R is r (mm), and the distance between the center of the ground bus 120R and the virtual ground channel 10A is D (mm).

Figure 2019046561
式（３）より、接地母線１２０Ｒの外径rを最大化することにより、リアンクタンスXECCを最小化し、循環電流を最大化できることが分かる。このため、図１に示す通り、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外径は、円１３０Ａに内接する外径を有する構成にしている。
Figure 2019046561
 From equation (3), it can be seen that by maximizing the outer diameter r of the ground bus 120R, the reactance X ECC can be minimized and the circulating current can be maximized. For this reason, as shown in FIG. 1, the outer diameters of the ground buses 120R, 120Y, and 120B are configured to have an outer diameter inscribed in the circle 130A.

このとき、循環電流IECCと、導線１１１Ｒに流れる電流Ic（電流１１１Ｒ１）との比の絶対値｜IECC/IC｜は、約３５％となる。このため、導線１１１Ｒに流れる電流Icの約３５％にあたる循環電流IECCを接地母線１２０Ｒに誘導できていることになる。 At this time, the absolute value | I ECC / I C | of the ratio between the circulating current I ECC and the current Ic (current 111R1) flowing through the conducting wire 111R is about 35%. For this reason, the circulating current I ECC corresponding to about 35% of the current Ic flowing through the conducting wire 111R can be induced to the ground bus 120R.

これは、導線１１１Ｙ及び接地母線１２０Ｙと、導線１１１Ｂ及び接地母線１２０Ｂとについても同様である。なお、このような循環電流IECCと電流Icとの比の絶対値｜IECC/IC｜は、電磁界シミュレーションで求めたものである。 The same applies to the conductive wire 111Y and the ground bus 120Y, and the conductive wire 111B and the ground bus 120B. Note that the absolute value | I ECC / I C | of the ratio between the circulating current I ECC and the current Ic is obtained by electromagnetic field simulation.

また、これは、導線１１１Ｙに流れる電流Ic及び接地母線１２０Ｙに流れる循環電流IECCと、導線１１１Ｂに流れる電流Ic及び接地母線１２０Ｂに流れる循環電流IECCとについても同様である。 This also applies to the current Ic flowing through the conductor 111Y and the circulating current I ECC flowing through the ground bus 120Y, and the current Ic flowing through the conductor 111B and the circulating current I ECC flowing through the ground bus 120B.

なお、以上では、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂが円１３０Ａに接するように、最大化された外径を有する形態について説明した。しかしながら、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外径は、もう少し小さくてもよい。   In the above description, the configuration has been described in which the grounded buses 120R, 120Y, and 120B have a maximized outer diameter so as to contact the circle 130A. However, the outer diameters of the ground buses 120R, 120Y, 120B may be a little smaller.

接地母線１２０Ｒ、１２０Ｙ、１２０Ｂは、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの外周面に沿って撚り合わされ、かつ、樹脂部材１５０が存在しない状態で、バインダ１３０によって支えられるような外径以上の外径を有していればよい。   The ground buses 120R, 120Y, 120B are twisted along the outer peripheral surface of the power transmission cables 110R, 110Y, 110B, and have an outer diameter that is larger than the outer diameter supported by the binder 130 in the state where the resin member 150 is not present. It only has to have.

図５は、実施の形態の変形例の電力ケーブル１００Ｍの断面を示す図である。図５に示す電力ケーブル１００Ｍの断面は、図１（Ｂ）に示す電力ケーブル１００の断面に対応する断面である。   FIG. 5 is a diagram illustrating a cross section of a power cable 100M according to a modification of the embodiment. The cross section of the power cable 100M illustrated in FIG. 5 is a cross section corresponding to the cross section of the power cable 100 illustrated in FIG.

電力ケーブル１００Ｍは、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ、接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭ、バインダ１３０Ｍ、防食層１４０Ｍ、及び樹脂部材１５０Ｍを含む。   The power cable 100M includes power transmission cables 110R, 110Y, 110B, ground buses 120RM, 120YM, 120BM, a binder 130M, an anticorrosion layer 140M, and a resin member 150M.

接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭは、３本の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの包絡閉曲線１１０Ｘよりも外側に突出する外径を有する。包絡閉曲線１１０Ｘは、断面視で中心線１０を中心とした３回対称の回転対称な位置に配置される３本の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの外周を覆う包絡閉曲線である。   The ground buses 120RM, 120YM, and 120BM have outer diameters that project outward from the envelope closed curve 110X of the three power transmission cables 110R, 110Y, and 110B. The envelope closed curve 110X is an envelope closed curve that covers the outer peripheries of the three power transmission cables 110R, 110Y, and 110B that are arranged at three-fold rotationally symmetric positions around the center line 10 in a cross-sectional view.

図５には、送電ケーブル１１０Ｒと１１０Ｙの外周の間と、送電ケーブル１１０Ｙと１１０Ｂの外周の間と、送電ケーブル１１０Ｂと１１０Ｒの外周の間とに、破線で包絡閉曲線１１０Ｘのうちの直線部分を破線で示す。包絡閉曲線１１０Ｘのうち、３本の破線以外の部分は、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの外周に沿っている。包絡閉曲線１１０Ｘは、三角形の頂点を送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの外周に沿って丸めたような形状である。   In FIG. 5, a straight line portion of the envelope closed curve 110 </ b> X is indicated by a broken line between the outer circumferences of the transmission cables 110 </ b> R and 110 </ b> Y, between the outer circumferences of the transmission cables 110 </ b> Y and 110 </ b> B, and between the outer circumferences of the transmission cables 110 </ b> B and 110 </ b> R. Shown in broken lines. Portions other than the three broken lines in the envelope closed curve 110X are along the outer periphery of the power transmission cables 110R, 110Y, and 110B. The envelope closed curve 110X has a shape obtained by rounding the apex of a triangle along the outer periphery of the power transmission cables 110R, 110Y, and 110B.

包絡閉曲線１１０Ｘよりも外側に突出する接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外径とは、接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外径が包絡閉曲線１１０Ｘに内接する場合の値よりも大きいことをいう。接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外径が包絡閉曲線１１０Ｘに内接する場合の値よりも大きければ、接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭがバインダ１３０によって支えられるからである。   The outer diameters of the ground buses 120RM, 120YM, and 120BM protruding outward from the envelope closed curve 110X mean that the outer diameters of the ground buses 120RM, 120YM, and 120BM are larger than the values in the case of being inscribed in the envelope closed curve 110X. This is because the ground buses 120RM, 120YM, and 120BM are supported by the binder 130 if the outer diameters of the ground buses 120RM, 120YM, and 120BM are larger than the values inscribed in the envelope closed curve 110X.

接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭがバインダ１３０によって支えられるとは、換言すれば、接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭが外側に押圧することによる張力がバインダ１３０に掛かることをいう。   That the ground buses 120RM, 120YM, and 120BM are supported by the binder 130, in other words, means that tension is applied to the binder 130 when the ground buses 120RM, 120YM, and 120BM are pressed outward.

このような接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外径は、３本の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの包絡閉曲線１１０Ｘよりも外側に突出する外径の中で最小の外径であり、実施の形態における接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭの最小の外径である。   The outer diameter of such ground buses 120RM, 120YM, and 120BM is the smallest outer diameter among the outer diameters that protrude outward from the envelope closed curve 110X of the three power transmission cables 110R, 110Y, and 110B. Are the minimum outer diameters of the ground buses 120RM, 120YM, and 120BM.

バインダ１３０Ｍは、図１及び図２に示すバインダ１３０と同様であるが、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ及び接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外側面を覆い、縛っている。バインダ１３０Ｍは、接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭが包絡閉曲線１１０Ｘよりも外側に突出する分だけ、外側に突出しているため、接地母線１２０には送電ケーブル１１０に向かって応力が働き、接地母線１２０により送電ケーブル１１０の表面を確実に接地することが可能となる。   The binder 130M is the same as the binder 130 shown in FIGS. 1 and 2, but covers and binds the outer surfaces of the power transmission cables 110R, 110Y, 110B and the ground buses 120RM, 120YM, 120BM. Since the binder 130M protrudes outward by the amount that the ground buses 120RM, 120YM, and 120BM protrude outward from the envelope closed curve 110X, stress acts on the ground bus 120 toward the power transmission cable 110, and the ground bus 120 The surface of the power transmission cable 110 can be reliably grounded.

防食層１４０Ｍは、図１及び図２に示す防食層１４０と同様であるが、バインダ１３０に重ねて設けられ、バインダ１３０を介して送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂ及び接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外側面を覆っている。   The anticorrosion layer 140M is the same as the anticorrosion layer 140 shown in FIGS. 1 and 2, but is provided so as to overlap the binder 130, and the power transmission cables 110R, 110Y, 110B and the ground buses 120RM, 120YM, 120BM are provided via the binder 130. Covers the outside surface.

樹脂部材１５０Ｍは、図１及び図２に示す樹脂部材１５０と同様であるが、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭとを覆うバインダ１３０Ｍ及び防食層１４０Ｍを外側に押圧することなく、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭとを覆った状態のバインダ１３０Ｍ及び防食層１４０Ｍの形状を保持するように配置されている。   The resin member 150M is the same as the resin member 150 shown in FIGS. 1 and 2, but presses the binder 130M and the anticorrosion layer 140M covering the power transmission cables 110R, 110Y, and 110B and the ground buses 120RM, 120YM, and 120BM outward. The binder 130M and the anticorrosion layer 140M in a state of covering the power transmission cables 110R, 110Y, and 110B and the ground buses 120RM, 120YM, and 120BM are disposed so as to maintain the shape.

なお、１１０Ｙ、１１０Ｂと接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭとを覆った状態のバインダ１３０Ｍ及び防食層１４０Ｍの形状は、１１０Ｙ、１１０Ｂと接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭとを覆う包絡閉曲線に等しい。   The shapes of the binder 130M and the anticorrosion layer 140M that cover the 110Y and 110B and the ground buses 120RM, 120YM, and 120BM are equal to the envelope closed curve that covers the 110Y and 110B and the ground buses 120RM, 120YM, and 120BM.

このような電力ケーブル１００Ｍでは、循環電流IECCと電流Icとの比の絶対値｜IECC/IC｜は、約２５％となる。このため、導線１１１Ｒに流れる電流Icの約２５％にあたる循環電流IECCを接地母線１２０ＲＭに誘導できていることになる。 In such a power cable 100M, the absolute value | I ECC / I C | of the ratio between the circulating current I ECC and the current Ic is about 25%. For this reason, the circulating current I ECC corresponding to about 25% of the current Ic flowing through the conducting wire 111R can be induced to the ground bus 120RM.

図６は、導線１１１Ｒ、１１１Ｙ、１１１Ｂに流れる電流Icと、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂに流れる循環電流IECCとの幾何学的中心位置を示す図である。 FIG. 6 is a diagram showing the geometric center position of the current Ic flowing through the conducting wires 111R, 111Y, 111B and the circulating current I ECC flowing through the ground buses 120R, 120Y, 120B.

導線１１１Ｒの電流Icの幾何学的中心位置は、接地母線１２０Ｒの同位相の循環電流IECCにより、近似的に導体１１１Ｒよりも中心線１０側（内側）になる。接地母線１２０Ｒの循環電流IECCが導体１１１の電流Icの３０％であれば、導線１１１Ｒの電流Icの幾何学的中心位置は、中心線１０から導体１１１Ｒまでの距離の７０％の距離の位置２０Ｒになる。これは、導線１１１Ｒ、１１１Ｙ、１１１Ｂの相間距離が実質的に短縮化されたことに等しい。 The geometric center position of the current Ic of the conducting wire 111R is approximately closer to the center line 10 side (inner side) than the conductor 111R due to the circulating current I ECC having the same phase of the ground bus 120R. If the circulating current I ECC of the ground bus 120R is 30% of the current Ic of the conductor 111, the geometric center position of the current Ic of the conductor 111R is a position that is 70% of the distance from the center line 10 to the conductor 111R. 20R. This is equivalent to the fact that the interphase distance between the conducting wires 111R, 111Y, and 111B is substantially shortened.

なお、３０％に設定したのは、図１及び図２に示す電力ケーブル１００における比の絶対値｜IECC/IC｜が約３５％であり、図５に示す電力ケーブル１００Ｍにおける比の絶対値｜IECC/IC｜が約２５％であるため、中間値を取ったものである。 The absolute value of the ratio | I ECC / I C | in the power cable 100 shown in FIG. 1 and FIG. 2 is about 35%, and the absolute value of the ratio in the power cable 100M shown in FIG. Since the value | I ECC / I C | is about 25%, an intermediate value is taken.

同様に、導線１１１Ｙの電流Icの幾何学的中心位置は、中心線１０から導体１１１Ｙまでの距離の７０％の距離の位置２０Ｙになる。また、導線１１１Ｂの電流Icの幾何学的中心位置は、中心線１０から導体１１１Ｂまでの距離の７０％の距離の位置２０Ｒになる。   Similarly, the geometric center position of the current Ic of the conducting wire 111Y is a position 20Y that is 70% of the distance from the center line 10 to the conductor 111Y. In addition, the geometric center position of the current Ic of the conducting wire 111B is a position 20R that is 70% of the distance from the center line 10 to the conductor 111B.

鉄損は、式（１）より理解できるように、電力ケーブルの相間距離Ｓが狭まると、略比例して鉄損が小さくなる。これは、導線１１１Ｒ、１１１Ｙ、１１１Ｂの中心間距離が、位置２０Ｒ、２０Ｙ、２０Ｂの中心間距離になることによって鉄損が小さくなるに相当する。   As can be understood from the equation (1), the iron loss decreases approximately in proportion to the distance S between the power cables. This is equivalent to the iron loss being reduced when the distance between the centers of the conductive wires 111R, 111Y, and 111B becomes the distance between the centers of the positions 20R, 20Y, and 20B.

図７は、電力ケーブル１００及び１００Ｍと、比較用の電力ケーブルとの接地母線の断面積、電流比、接地母線の発熱量、鋼管５０の外表面での磁界、及び鉄損を示す図である。   FIG. 7 is a diagram showing the cross-sectional area of the ground buses of the power cables 100 and 100M and the comparative power cable, the current ratio, the heat generation amount of the ground buses, the magnetic field on the outer surface of the steel pipe 50, and the iron loss. .

接地母線の断面積は、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの断面積を１００％とした場合の割合で表す。電流比は、循環電流IECCと電流Icとの比の絶対値｜IECC/IC｜を表す。接地母線の発熱量は、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの断面積を１倍とした場合の割合で示す。鋼管５０の外表面での磁界は、比較用の電力ケーブルにおける磁界を１００％とした場合の割合で表す。鉄損は、比較用の電力ケーブルにおける鉄損を１００％とした場合の割合で表す。 The cross-sectional area of the ground bus is expressed as a ratio when the cross-sectional areas of the ground buses 120R, 120Y, and 120B are 100%. The current ratio represents the absolute value | I ECC / I C | of the ratio between the circulating current I ECC and the current Ic. The amount of heat generated by the ground bus is shown as a ratio when the cross-sectional area of the ground bus 120R, 120Y, 120B is set to 1 time. The magnetic field on the outer surface of the steel pipe 50 is expressed as a ratio when the magnetic field in the comparative power cable is 100%. The iron loss is expressed as a ratio when the iron loss in the power cable for comparison is 100%.

図７に示すように、接地母線の断面積は、比較用の電力ケーブルは、接地母線を含まないため０％であり、電力ケーブル１００は１００％であり、電力ケーブル１００Ｍは２７％である。   As shown in FIG. 7, the cross-sectional area of the ground bus is 0% because the comparative power cable does not include the ground bus, the power cable 100 is 100%, and the power cable 100M is 27%.

また、電流比については、比較用の電力ケーブルは、接地母線を含まないため０％であり、電力ケーブル１００は３５％であり、電力ケーブル１００Ｍは２５％である。これは、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂ及び１２０ＲＭ、１２０ＹＭ、１２０ＢＭの断面積が大きいほど、電流比が大きくなることを示している。   The current ratio is 0% because the comparative power cable does not include the ground bus, the power cable 100 is 35%, and the power cable 100M is 25%. This indicates that the current ratio increases as the cross-sectional areas of the ground buses 120R, 120Y, 120B and 120RM, 120YM, 120BM increase.

また、接地母線の発熱量については、比較用の電力ケーブルは、接地母線を含まないため０倍であり、電力ケーブル１００は１倍であり、電力ケーブル１００Ｍは１．９倍である。これは、接地母線１２０Ｒ，１２０Ｙ，１２０Ｂの方が接地母線１２０ＲＭ，１２０ＹＭ，１２０ＢＭに比べて循環電流が大きいにも関わらず、断面積が大きいため抵抗が低く、発熱量が小さくなることを示している。   The heat generation amount of the ground bus is 0 times because the comparative power cable does not include the ground bus, the power cable 100 is 1 time, and the power cable 100M is 1.9 times. This shows that although the ground buses 120R, 120Y, 120B have larger circulating currents than the ground buses 120RM, 120YM, 120BM, the cross-sectional area is large, so the resistance is low and the heat generation amount is small. Yes.

また、鋼管５０の外表面での磁界については、比較用の電力ケーブルは１００％であり、電力ケーブル１００は８７％であり、電力ケーブル１００Ｍは９０％である。これより、接地母線１２０ＲＭ，１２０ＹＭ，１２０ＢＭにながれる循環電流の大きい方が、３相の幾何学的な電流位置の距離が近づき、また、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの相間距離が短いほど、磁界が小さくなることを示している。   Regarding the magnetic field on the outer surface of the steel pipe 50, the power cable for comparison is 100%, the power cable 100 is 87%, and the power cable 100M is 90%. Accordingly, the larger the circulating current flowing to the ground buses 120RM, 120YM, and 120BM, the closer the distance between the three-phase geometric current positions, and the shorter the interphase distance between the transmission cables 110R, 110Y, and 110B, the shorter the magnetic field. Indicates that becomes smaller.

また、鉄損については、磁界の約二乗に比例して発生するが、磁界シミュレーションの結果、比較用の電力ケーブルは１００％であり、電力ケーブル１００は７０％であり、電力ケーブル１００Ｍは８０％である。   Iron loss occurs in proportion to the square of the magnetic field. As a result of the magnetic field simulation, the power cable for comparison is 100%, the power cable 100 is 70%, and the power cable 100M is 80%. It is.

このように、電力ケーブル１００及び１００Ｍは、比較用の電力ケーブルに比べて、電流比が増大し、鋼管５０の外表面での磁界が低減され、鉄損が低減されていることが分かった。   Thus, it was found that the power cables 100 and 100M have an increased current ratio, a reduced magnetic field on the outer surface of the steel pipe 50, and reduced iron loss compared to the comparative power cable.

以上、実施の形態によれば、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂは、断面視で中心線１０を中心とした３回対称の回転対称な位置関係に配置した状態で円１３０Ａに内接する外径を有する。円１３０Ａは、断面視で鋼管５０の内部に敷設可能な最大の電力ケーブルの包絡円の半径からバインダ１３０及び防食層１４０の厚さを除いた半径を有する円である。   As described above, according to the embodiment, the power transmission cables 110R, 110Y, and 110B have outer diameters that are inscribed in the circle 130A in a state of being arranged in a three-fold rotationally symmetric positional relationship centered on the center line 10 in a cross-sectional view. Have. The circle 130A is a circle having a radius obtained by removing the thickness of the binder 130 and the anticorrosion layer 140 from the radius of the envelope circle of the maximum power cable that can be laid inside the steel pipe 50 in a cross-sectional view.

送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの各々は、導線１１１、導線スクリーン１１２、絶縁層１１３、絶縁スクリーン１１４、及びベッディング１１５を有する構成であり、なるべく導線１１１の断面積を稼げるように、必要最小限の構成にしてある。このようにして、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの導線１１１（１１１Ｒ、１１１Ｙ、１１１Ｂ）の断面積を最大化している。   Each of the power transmission cables 110R, 110Y, and 110B has a configuration including a conductive wire 111, a conductive wire screen 112, an insulating layer 113, an insulating screen 114, and a bedding 115. It is configured. In this way, the cross-sectional area of the conducting wire 111 (111R, 111Y, 111B) of the power transmission cables 110R, 110Y, 110B is maximized.

また、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外側面に絶縁層等の遮蔽物を設けずに、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂが円１３０Ａに接する外径を有する。このようにして、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外径を最大化している。   In addition, the ground buses 120R, 120Y, 120B have an outer diameter in contact with the circle 130A without providing a shield such as an insulating layer on the outer surface of the ground buses 120R, 120Y, 120B. In this way, the outer diameters of the ground buses 120R, 120Y, 120B are maximized.

また、実施の形態の変形例の電力ケーブル１００Ｍでは、接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭは、３本の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの包絡閉曲線１１０Ｘよりも外側に突出する外径を有する。   Moreover, in the power cable 100M of the modification of the embodiment, the ground buses 120RM, 120YM, and 120BM have outer diameters that protrude outward from the envelope closed curve 110X of the three power transmission cables 110R, 110Y, and 110B.

そして、上述のような送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０Ｒ、１２０Ｙ、１２０Ｂとを用いることにより、又は、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂと接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭとを用いることにより、
送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの導線１１１Ｒ、１１１Ｙ、１１１Ｂに流れる電流Icの幾何学的中心位置を約３０％程内側（中心線１０側）にオフセットさせることができる。 Then, by using the power transmission cables 110R, 110Y, 110B and the ground buses 120R, 120Y, 120B as described above, or by using the power transmission cables 110R, 110Y, 110B and the ground buses 120RM, 120YM, 120BM,
The geometric center position of the current Ic flowing through the conducting wires 111R, 111Y, 111B of the power transmission cables 110R, 110Y, 110B can be offset to the inner side (center line 10 side) by about 30%.

従って、送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂでの鉄損を低減し、全体での損失を３０％程度低減した電力ケーブル１００及び１００Ｍを提供することができる。すなわち、鉄損を抑制するとともに、送電電力を増大させた電力ケーブル１００及び１００Ｍを提供することができる。   Therefore, it is possible to provide the power cables 100 and 100M that reduce the iron loss in the power transmission cables 110R, 110Y, and 110B and reduce the overall loss by about 30%. That is, it is possible to provide power cables 100 and 100M that suppress iron loss and increase transmission power.

なお、以上では、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂの外径が、円１３０Ａに内接する外径である形態と、接地母線１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外径が、３本の送電ケーブル１１０Ｒ、１１０Ｙ、１１０Ｂの包絡閉曲線１１０Ｘよりも外側に突出する外径の中で最小の外径である形態とについて説明した。   In the above, the outer diameter of the ground buses 120R, 120Y, 120B is the outer diameter inscribed in the circle 130A, and the outer diameters of the ground buses 120RM, 120YM, 120BM are the three power transmission cables 110R, 110Y, The form which is the smallest outer diameter among the outer diameters protruding outward from the envelope closed curve 110X of 110B has been described.

しかしながら、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂ、又は、１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外径は、これらの外径の間の任意の値であってもよい。すなわち、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂ、又は、１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外径は、包絡閉曲線１１０Ｘよりも外側に突出する外径であって、かつ、円１３０Ａに内接する外径以下であればよい。   However, the outer diameter of the ground buses 120R, 120Y, 120B, or 120RM, 120YM, 120BM may be any value between these outer diameters. That is, the outer diameter of the ground buses 120R, 120Y, 120B, or 120RM, 120YM, 120BM is an outer diameter that protrudes outward from the envelope closed curve 110X and is equal to or smaller than the outer diameter inscribed in the circle 130A. Good.

換言すれば、接地母線１２０Ｒ、１２０Ｙ、１２０Ｂ、又は、１２０ＲＭ、１２０ＹＭ、１２０ＢＭの外径は、包絡閉曲線１１０Ｘよりも外側に突出する外径であって、円１３０Ａに収まる外径であればよい。接地母線１２０Ｒ、１２０Ｙ、１２０Ｂが円１３０Ａに接する外径を有することは、円１３０Ａに収まる外径のうちで最大の外径を有する場合に相当する。   In other words, the outer diameter of the ground buses 120R, 120Y, 120B, or 120RM, 120YM, 120BM may be an outer diameter that protrudes outward from the envelope closed curve 110X and that fits in the circle 130A. The fact that the ground buses 120R, 120Y, and 120B have an outer diameter in contact with the circle 130A corresponds to the case where the outer diameter that fits in the circle 130A has the largest outer diameter.

以上、本発明の例示的な実施の形態の電力ケーブルについて説明したが、本発明は、具体的に開示された実施の形態に限定されるものではなく、特許請求の範囲から逸脱することなく、種々の変形や変更が可能である。   The power cable of the exemplary embodiment of the present invention has been described above. However, the present invention is not limited to the specifically disclosed embodiment, and does not depart from the scope of the claims. Various modifications and changes are possible.

５０ 鋼管
１００、１００Ｍ 電力ケーブル
１１０Ｒ、１１０Ｙ、１１０Ｂ 送電ケーブル
１１１ 導線
１１２ 導線スクリーン
１１３ 絶縁層
１１４ 絶縁スクリーン
１１５ ベッディング
１２０Ｒ、１２０Ｙ、１２０Ｂ、１２０ＲＭ、１２０ＹＭ、１２０ＢＭ 接地母線
１３０、１３０Ｍ バインダ
１４０、１４０Ｍ 防食層
１５０、１５０Ｍ 樹脂部材 50 Steel pipe 100, 100M Power cable 110R, 110Y, 110B Transmission cable 111 Conductor 112 Conductor screen 113 Insulating layer 114 Insulating screen 115 Beding 120R, 120Y, 120B, 120RM, 120YM, 120BM Ground bus 130, 130M Binder 140, 140M Anticorrosion layer 150 , 150M resin member

Claims (5)

基準電位点に接続される鋼管の内部に敷設される電力ケーブルであって、
三相交流電力を伝送する導電線と、前記導電線を被覆する絶縁層と、前記絶縁層を被覆する半導電層とを有する３本の送電ケーブルであって、断面視で前記３本の送電ケーブルの中心に対する３回対称の回転対称な位置において互いの前記半導電層同士が接した状態で配置される３本の送電ケーブルと、
３本の接地母線であって、それぞれが前記３本の送電ケーブルのうちの隣り合う２本の外周面に接して、前記中心に対する３回対称の回転対称な位置に配置される３本の接地母線と、
前記３本の接地母線及び前記３本の送電ケーブルの外側面を覆うバインダと、
前記バインダに重ねて配置されるジャケットと
を含み、
前記３本の送電ケーブルは、断面視で前記鋼管の内部に敷設可能な最大の電力ケーブルの包絡円の半径から前記バインダ及び前記ジャケットの厚さを除いた半径を有する第１円に内接する外径を有し、
前記３本の接地母線は、断面視で３本の送電ケーブルの包絡閉曲線よりも突出し、前記第１円に収まる外径を有する、電力ケーブル。 A power cable laid inside a steel pipe connected to a reference potential point,
Three power transmission cables having a conductive wire for transmitting three-phase AC power, an insulating layer for covering the conductive wire, and a semiconductive layer for covering the insulating layer, wherein the three power transmission cables in a cross-sectional view Three power transmission cables arranged in a state where the semiconductive layers are in contact with each other at a rotationally symmetric position that is three-fold symmetric with respect to the center of the cable;
Three ground buses, each of which is in contact with two adjacent outer peripheral surfaces of the three power transmission cables and arranged in a rotationally symmetric position of three-fold symmetry with respect to the center With busbars,
A binder that covers the outer surfaces of the three ground buses and the three power transmission cables;
A jacket disposed over the binder,
The three power transmission cables are externally inscribed in a first circle having a radius excluding the thickness of the binder and the jacket from the radius of the envelope circle of the largest power cable that can be laid in the steel pipe in a cross-sectional view. Has a diameter,
The three ground buses protrude from an envelope closed curve of the three power transmission cables in a cross-sectional view and have an outer diameter that fits in the first circle. 前記３本の接地母線の外径は、前記３本の接地母線の外周面が前記第１円に接する外径である、請求項１記載の電力ケーブル。   2. The power cable according to claim 1, wherein an outer diameter of the three ground bus bars is an outer diameter at which an outer peripheral surface of the three ground bus bars is in contact with the first circle. 前記３本の接地母線の各々は、外周面に遮蔽物又は防食層を有さず、前記３本の送電ケーブルのうちの隣り合う２本の外周面に直接接触しており、かつ、前記３本の接地母線の各々の両端は、前記基準電位点と電位が等しい電位点に接続される、請求項１又は２記載の電力ケーブル。   Each of the three ground buses does not have a shield or an anticorrosion layer on the outer peripheral surface, is in direct contact with two adjacent outer peripheral surfaces of the three power transmission cables, and the 3 The power cable according to claim 1 or 2, wherein both ends of each of the ground buses are connected to a potential point having the same potential as the reference potential point. 前記３本の送電ケーブルは、断面視で前記中心を通る中心軸を中心とする３回対称の回転対称な位置関係を保ちながら、前記中心軸の周囲に撚り合わされる、請求項１乃至３のいずれか一項記載の電力ケーブル。   The three power transmission cables are twisted around the central axis while maintaining a three-fold rotationally symmetric positional relationship around the central axis passing through the center in a cross-sectional view. The power cable according to any one of the above. 前記３本の接地母線は、それぞれ、前記３本の送電ケーブルのうちの隣り合う２本の外周面に接した状態で、断面視で前記中心軸を中心とする３回対称の回転対称な位置関係を保ちながら、前記３本の接地母線の周囲に撚り合わされる、請求項４記載の電力ケーブル。   The three ground buses are in contact with two adjacent outer peripheral surfaces of the three power transmission cables, and are rotationally symmetric positions having a three-fold symmetry about the central axis in a sectional view. The power cable according to claim 4, wherein the power cable is twisted around the three ground buses while maintaining a relationship.
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